The use of concrete median barriers between opposing lanes of interstate highways and along other roadways has been a major advancement in the reduction of head-on collisions and other accidents between approaching vehicles on the roadways. The Type 50 concrete barrier is primarily used because of its inclined lower surface on each side of the barrier adjacent the roadway for straightening a front vehicle wheel which rides up on the barrier when the vehicle accidentally approaches the barrier at a small angle of incidence. However, when a vehicle impacts the concrete barrier at a high angle of incidence, the high friction hard surface of the concrete barrier and the higher impact force commonly result in significantly greater damage to the vehicle and to the barrier as well as greater injuries to the vehicle driver and passengers in the vehicle. In fact, some impacts will either crack the concrete barrier and/or cause the vehicle to spin out of control, sometimes resulting in accidents with other vehicles moving on the roadway.
There have been several systems proposed or used for reducing the damages to motor vehicles and injuries to their occupants when the vehicles accidentally impact the concrete median barriers. One system is known as the PEDS Barrier which has been used along vehicle race tracks and incorporates a continuous series of vertical cylinders. Each cylinder has a diameter of about 16xe2x80x3 and is constructed of a high density polyethylene. The cylinders are positioned adjacent the concrete wall or barrier and are covered by an overlapping sheet of high density polyethylene material. The cylinders are secured to the barrier by longitudinally spaced cables extending around the barrier, and the sheet is attached by bolts to the cylinders. The cost of this system is substantial and is therefore primarily used on concrete walls or barriers at race tracks adjacent the seating area for patrons.
U.S. Pat. No. 4,681,302 and U.S. Pat. No. 5,054,954 disclose other forms of energy absorbing roadway barriers which involve formed or molded sheets or bodies of plastics material to form a container defining a chamber. The chamber is filled with a liquid or a filler material which can absorb impact forces, sometimes by being forced out of the container when the container is crushed by an impacting vehicle.
With any such form of energy absorbing or dissipating system which is constructed to form or modify highway median barriers, it is highly desirable for the system to be of economical construction and to be easily and quickly installed along the highway or on an existing concrete barrier so that disruption of traffic on the adjacent roadway lane is minimized. It has also been found desirable for the device to dissipate or distribute the energy of an impacting vehicle and to minimize the friction between the device and the vehicle and guide the vehicle so that the vehicle is redirected back into the adjacent traffic lane with a minimum loss of speed in order to reduce vehicle accidents and injuries to occupant in the vehicles. It is further desirable for the energy dissipating system or device to withstand impacts at high angles of incidence and from high speed vehicles without damaging the device or the concrete barrier so that maintenance on the barrier and device is minimized.
The present invention is directed to an improved energy dissipating system or device which is ideally suited for mounting on a concrete roadway barrier and which provides all of the desirable advantages mentioned above. That is, the device of the invention helps to maintain control of a vehicle which impacts a barrier and is effective to reduce damage to the vehicle and to the concrete barrier, especially when the vehicle impacts at a higher speed over 50 mph and/or at a higher angle of incidence such as up to thirty degrees. The system or device of the invention is also economical in construction, may be quickly and easily attached to an existing concrete barrier and minimizes the loss of speed of an impacting vehicle so that the driver may return the vehicle to the adjacent lane without disrupting traffic in the lane.
In accordance with one embodiment of the invention, an energy dissipating system or device includes a flexible sheet of heavy gauge plastics material having a low coefficient of friction. The sheet has a width of about 24xe2x80x3 and a length of about 60xe2x80x3. The sheet has upper and lower edge portions which are attached or secured to a side surface of a concrete barrier by longitudinally spaced concrete anchors and screws, and the down lane end portion of each sheet overlaps the up lane end portion of the adjacent sheet. A longitudinally extending cavity is defined between the sheet and the side surface of the concrete barrier, and an elongated resilient energy dissipating member extends longitudinally within the cavity. In one form, the energy dissipating member comprises an elongated plastic inner tube having a 3xe2x80x3 diameter and confined within a similar outer tube having a 4xe2x80x3 diameter. In another embodiment, an energy dissipating member comprises helically extending resilient plastic turns or coils disposed between the inner and outer tubes, and the inner tube is formed by a wrapped sheet of plastics material. A plurality of tube sets or assemblies or other forms of resilient energy dissipating members may also be confined within the cavity.
Other features and advantages of the invention will be apparent from the following description, the accompanying drawing and the appended claims.